In computer systems such as a high-density server, a plurality of logical units are mounted in one housing or motherboard. Each logical unit includes a CPU chip that integrates one or a plurality of CPU cores and an input/output circuit, a plurality of memory chips, and an interface apparatus to the outside. In such a computer system, a first DC voltage is supplied to the plurality of logical units from an external power supply unit, and a power supply apparatus that is a DC voltage conversion device performs voltage conversion of the first DC voltage to generate second and third DC voltages and supplies the second and third DC voltages to the CPU chip, memory chip, external interface apparatus, and the like in each logical unit.
By supplying the first DC voltage to each logical unit at a relatively high voltage from an external power supply unit, converting the first DC voltage into second and third DC voltages that are lower than the first DC voltage with a power supply apparatus located in a vicinity of each logical unit, and supplying the second and third DC voltages to LSI chips and the like in each logical unit as power supply voltages, power loss due to an IR drop in power supply voltage wiring from the external power supply unit to the logical units is reduced.
A general computer system is configured such that power can be turned on/off on a per logical unit basis. Therefore, each logical unit is provided with a dedicated power supply apparatus that supplies a power supply voltage to an LSI chip and the like that is mounted to the logical unit. As a result, by summing up output voltages of a power supply apparatus that is exclusively provided for a logical unit, power consumption of each logical unit is measured. Measuring a power consumption is disclosed in Japanese Patent Application Laid-open No. 2012-98135, Japanese Patent Application Laid-open No. H10-103737 and Japanese Patent Application Laid-open No. H02-38975.